1. Field of the Invention
The present invention relates to a wireless communication system having an RLC layer of a transparent mode and data processing method in the same.
2. Background of the Related Art
Many efforts are made to research and develop communication technologies providing access to multimedia without spatiotemporal limitations. The development of these technologies in addition to the development of digital data processing and transmission technologies will help unify wireless and wired communications and help realize a real-time global data communication system. Developments in digital data processing and data transmission increasingly enable users to access to information, through still images stored on a network, the real-time transmission of moving pictures, wired/wireless communication, and conventional voice communication. And, IMT-2000 will be included in such access technologies.
A Radio Link Control (RLC) layer is a second layer of 3GPP and corresponds to a second layer of an OSI 7-layered model, as a protocol layer controlling a data link. Species of RLC entities used for 3GPP are mainly divided into a transparent (Tr) mode having no RLC header and a non-transparent (Ntr) mode.
The Ntr mode is further divided into an unacknowledged mode (UM mode), having no acknowledged (ACK) signal from the receiver side, and an acknowledged mode (AM) having an acknowledged signal from the receiver side. Therefore, the modes of RLC which are presently used are Tr, UM, and AM.
FIG. 1 illustrates a diagram of a data transmission apparatus in a wireless communication system having an RLC layer of a Tr mode. A Tr mode not attached to an RLC header is simpler than an entity structure in an NTr mode.
Based on a radio interface 100, a data transmission apparatus having an RLC layer 101 of a Tr mode carries out segmentation through a segmentation part 102 so as to turn service data units (SDUs), which come down from a higher layer, into protocol data units (PDUs) having a uniform size.
The segmented protocol data units are stored in a transmission buffer 103 and then sent down to a medium access control (MAC) layer 104 through a logical channel. When the RLC layer 101 transmits the PDUs to the MAC layer 104, the PDUs are transmitted by transmission time interval (TTI).
The RLC layer 101 transmits the number of PDUs requested by the MAC layer 104. For this purpose, the MAC layer 104 informs the RLC layer 101 of the number of PDUs to send during each TTI, through its status information (MAC-STATUS-IND primitive).
In response to the information about the number of PDUs to send with each TTI, the RLC layer 101 transmits the number of PDUs corresponding to the number requested by the MAC layer 104. These PDUs are transmitted from the transmission buffer 103 to the MAC layer 104.
The PDUs are transmitted to a data receiver device 105 of a wireless communication system having the RLC layer of the Tr mode based on the radio interface 100. The receiver device 105 stores the PDUs received on the basis of the radio interface 100 in a receiver buffer 106 for a while. The receiver device 105 then sends up the PDUs by SDU unit to a higher layer, whenever PDUs constructing a complete SDU are received. Namely, the protocol data units are reassembled by SDU unit in an assembly part 107 so as to be delivered to the higher layer.
The above-mentioned related art has the problems or disadvantages as follows.
First, the MAC layer 104 of the transmission device multiplexes the PDUs received from various RLC layers and then transmits the multiplexed PDUs to a physical layer PHY through a transport channel. In this case, in order to improve an efficiency of transmission, the MAC layer 104 adjusts the number of the PDUs received from each of the RLC layers differently with each TTI.
However, it is difficult to secure the transmission efficiency improvement by means of adjusting only the number of PDUs with every TTI. In order to improve the transmission efficiency, it is desirable that a PDU size as well as the number of PDUs received from the respective RLC layers, with every TTI, be adjusted. Yet, it is very difficult to adjust the PDU size with every TTI in the related art.
Second, the data transmission device of the related art carries out segmentation on the SDUs based on PDUs of a uniform size and then stores the PDUs in the transmission buffer 103. If a PDU having a different size is to be transmitted, the PDUs stored in the transmission buffer 103 have to be reassembled into SDUs again.
Successively, the reassembled SDUs are segmented into new PDUs having the size requested by the MAC layer 104. Then, the re-segmented PDUs are transmitted to the MAC layer 104.
For the above-mentioned case, a process or means for reassembling the PDUs, stored in the transmission buffer 103, into SDUs is required. Moreover, a process of segmenting the reassembled SDUs into PDUs having the size requested by the MAC layer 104 is required as well. Therefore, the construction of the RLC layer becomes complicated and a transmission processing time of the protocol data units is increased.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.